Skip to content
RADON411

Locations and reports

Radon Levels in Benewah County, Idaho

EPA puts Benewah County in Zone 1, its highest radon zone, and only 29 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    21.3%

    19.5 pts below ID

    Benewah
    21.3%
    Idaho
    40.8%

    47 tests, 2007 to 2016

  • Median result

    2.0pCi/L

    Below action level

    Benewah
    2.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2007 to 2016

  • Tests reported

    47

    31st of 40 by tests

    Benewah
    47
    Ada
    2,966

    Reported to CDC before any fix, 2007 to 2016

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Idaho

    31 of 40

    Lowest quarter

    Benewah
    21.3%
    Bear Lake
    78.1%

    By share, of 40 with 30+ tests

Read a result for Benewah County

Starts at Benewah County's median, 2.0 pCi/L

2.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 2.0 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Benewah County's median reported result, 2007 to 2016.

Interpret this readingWhat a fix costs

The data

Benewah County, At a glance

Benewah County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Benewah County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 90% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Benewah County, 2008 to 2017, laboratory

CDC holds 29 reported tests for Benewah County over the 2008 to 2017 laboratory totals, with a median of 2.4 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Benewah County beside the counties around it is how this page reads it.

What these figures count

Only 29 tests were reported to CDC for Benewah County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Benewah County, Compared

Benewah County radon figures, compared

Calculated by Radon411

Benewah County's 47 reported tests over the 2007 to 2016 laboratory totals had a middle value of 2.0 pCi/L and a maximum of 10.7 pCi/L, and 21.3% reached 4 pCi/L. Idaho as a whole (44 Idaho counties, pooled) comes to 40.8%: 19.5 points higher than here.

The newest figure, over the 2008 to 2017 laboratory totals, counts only 29 tests (31.0% at or above 4 pCi/L), too few to compare, so this reading uses the 47-test figure.

Among its state's counties it ranks 31st of 40 Idaho counties with 30 or more tests for the same period. Statewide for the same period, Bear Lake County reported the highest share (78.1%) and Payette County the lowest (5.5%).

Below the action level, 23 tests (48.9%) came in under 2 pCi/L, against 32.2% statewide, and 14 tests (29.8%) fell between 2 and 4, against 27.0% statewide. CDC's ten-year totals for Benewah County went from 47 tests (2005 to 2014) to 29 (2008 to 2017), the share going from 19.1% to 31.0%.

EPA's 1993 zone map puts Benewah County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 90% of the county's land high radon potential.

Next door, the shares run from 26.4% in Latah County to 60.7% in Kootenai County.

Benewah County against Idaho, the United States and nearby counties, 2007 to 2016, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Benewah County
Benewah County4721.3%2.0 pCi/LThis county
Idaho, pooled44 counties, pooled12,49540.8%Not pooled+19.5 points
United States, pooled2,666 counties, pooled1,939,02535.8%Not pooled+14.5 points
Bear Lake Countyhighest in the state3278.1%6.5 pCi/L+56.8 points
Payette Countylowest in the state555.5%1.3 pCi/L−15.8 points
Kootenai County, IDborders it2,83460.7%5.9 pCi/L+39.4 points
Shoshone County, IDborders it8759.8%4.5 pCi/L+38.5 points
Spokane County, WAborders it2,97941.6%3.0 pCi/L+20.3 points
Whitman County, WAborders it4827.1%1.6 pCi/L+5.8 points
Latah County, IDborders it14026.4%1.8 pCi/L+5.1 points
Where Benewah County's reported results fell, 2007 to 2016, laboratory, beside Idaho and the United States
ResultBenewah County testsBenewah County shareIdaho shareU.S. shareAgainst Idaho
Under 2 pCi/L2348.9%32.2%39.6%+16.7 points
2 to 4 pCi/L1429.8%27.0%24.6%+2.8 points
4 pCi/L and above1021.3%40.8%35.8%−19.5 points
Benewah County ranked among the 40 Idaho counties with 30 or more tests, by share at or above 4 pCi/L, 2007 to 2016, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Boise County26 of 405525.5%2.0 pCi/L
Ada County27 of 402,96624.7%2.4 pCi/L
Clearwater County28 of 404124.4%1.3 pCi/L
Twin Falls County29 of 4030424.3%2.3 pCi/L
Valley County30 of 4011624.1%2.2 pCi/L
Benewah County31 of 404721.3%2.0 pCi/L
Washington County32 of 406520.0%2.3 pCi/L
Owyhee County32 of 403520.0%1.8 pCi/L
Nez Perce County34 of 4015018.7%2.0 pCi/L
Boundary County35 of 404418.2%1.9 pCi/L
Gem County36 of 408517.6%1.9 pCi/L
Benewah County ten-year laboratory totals, against Idaho's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIdaho, pooledChange from the row before
2008 to 20172931.0%2.4 pCi/L10.7 pCi/L41.5%+9.7 points
2007 to 20164721.3%2.0 pCi/L10.7 pCi/L40.8%+3.9 points
2006 to 20154617.4%1.9 pCi/L10.7 pCi/L41.3%−1.7 points
2005 to 20144719.1%1.7 pCi/L10.7 pCi/L41.1%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Benewah County, Geology

The ground under Benewah County

Predicted

Most of the ground under Benewah County is one class on USGS's geologic map: 90.4% of its land is high radon potential, with 9.6% moderate. The map puts 90.4% of Benewah County in the area it calls Northern Rocky Mountain Province and 9.6% in Palouse Hills. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).

USGS's geologic areas under Benewah County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern Rocky Mountain ProvinceDiorite and granite of the Idaho batholith.High1290.4%
Palouse HillsBasalt, locally covered by loess.Moderate109.6%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Benewah County beside the ground around it

Benewah County has more high-potential ground than Idaho as a whole: 90.4% of its land against 50.7%. Of the 5 counties that border it, 2 have more high-potential ground, Shoshone County the most at 100%.

Share of land by USGS radon potential: Benewah County, the 5 counties bordering it and Idaho
AreaEPA zoneLow potentialModerate potentialHigh potential
Benewah CountyZone 1None9.6%90.4%
Latah CountyZone 131.0%12.1%56.9%
Kootenai CountyZone 1None8.5%91.5%
Shoshone CountyZone 1NoneNone100%
Spokane County, WAZone 1None56.7%43.3%
Whitman County, WAZone 2None99.1%0.9%
Idaho44 counties, pooled by land areaVaries8.0%41.3%50.7%

The map rates the ground, not the air in any home.

Local help

Benewah County, Local resources

Radon testing and mitigation in Benewah County

What Idaho's program says
Phone
800-445-8647
Email
radon@dhw.idaho.gov

What it means

Benewah County, Questions

Questions about radon in Benewah County

Are radon levels high in Benewah County?

Over the 2008 to 2017 laboratory totals, 31.0% of the radon tests reported to CDC for Benewah County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.4 pCi/L. Of 40 Idaho counties with 30 or more tests for the same period, 30 reported a higher share; pooled, the state comes to 40.8%.

Which counties border Benewah County?

Benewah County borders 5 counties: Latah County, ID, Kootenai County, ID, Shoshone County, ID, Spokane County, WA and Whitman County, WA.

Products

Benewah County, Products

Testing a home in Benewah County

In Benewah County, 21.3% of 47 tests reported to CDC over the 2007 to 2016 laboratory totals reached 4 pCi/L, against 40.8% pooled across Idaho. In Zone 1 the year-round level in Benewah County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Benewah County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Benewah County

Explore

Benewah County, Bordering counties

Counties bordering Benewah County

Calculated by Radon411

Benewah County, Cities and towns

Cities and towns in Benewah County

Benewah County is growing: the Census Bureau puts it at 10,508 residents on July 1, 2025, up 9.7% from 9,580 in 2020. That works out to 14 people per square mile of land. Its largest town, St. Maries, has 2,457 residents, 23.4% of the total. Together its 3 incorporated places hold 35.1% of those residents; the other 64.9% live outside any of them. CDC's 47 reported tests for 2007 to 2016 work out to 4.5 per 1,000 residents (2025 estimate), close to Idaho's 6.2.

From St. Maries to Tensed, CDC publishes no figure by town: each reads Benewah County's.

The cities and towns in Benewah County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
St. Maries2,457+3.7%23.4%
Plummer1,130+11.3%10.8%
Tensed99+13.8%0.9%

3 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Benewah County, Homes

Homes in Benewah County

Of Benewah County's 4,706 homes, 73% are detached houses, against 74% across Idaho; 20% are mobile homes. The homes are older than Idaho's as a whole: half were built before 1978 (1990 for Idaho), and 22% date from before 1960. Owners live in 76% of the occupied homes (Idaho: 72%), so for most households a test and a fix are their own to order.

Homes in Benewah County, Idaho, 2019 to 2023
HomesBenewah CountyIdaho
Housing units4,706776,683
Detached houses73%74%
In buildings of 5 or more4%9%
Mobile homes20%7%
Built before 196022%18%
Built since 200015%35%
Middle year built19781990
Owner-occupied76%72%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.